[Bibliographic review. The role of hypoestrogenism in postmenopausal osteoporosis--new perspectives].

Estrogen deficiency following menopause results in a significative bone loss, which is thought to be the result of an imbalance in bone remodeling process between formation activity and resorption, where the later is functionally higher than normal and could develop osteopenia or osteoporosis type I. Although it has been made a lot of scientific investigations to explain the way by hypoestrogenism affect skeleton, the renal mechanism remains unclear and it seems to be multifactorial. Therefore, the purpose of this review is to analyze the new perspectives about the effects of serum estradiol levels on bone tissue; special emphasize is made concerning the role of: estrogen receptors, cytokines, RANKL/RANK/OPG system, PTH and PTHrP, bone turnover markers, osteocytes apoptosis, estrogens serum levels and its metabolic pathways.